Pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer, is one of the deadliest forms of cancer. Poor survival rates are largely due to the late stage at which PDAC is diagnosed and a lack of effective therapies. The long-term goal of this research program is to discover new therapeutic approaches and drug combinations for the treatment of PDAC and other incurable cancers. Previous studies by our group identified a new class of protein disulfide isomerase (PDI) inhibitor with activity in a variety of solid and hematological cancer types including PDAC. PDIs are emerging oncology targets that play a critical role in the proper folding of newly synthesized proteins. PDIs are overexpressed in a variety of tumor types and are attractive oncology targets. In an unbiased screen of FDA-approved oncology drugs, we found this new class of drug could dramatically enhance the activity of histone deacetylase (HDAC) inhibitors with the strongest synergy being observed in PDAC models. The specific objectives of this study are: (1) to uncover the molecular mechanism responsible for the remarkable synergy between PDI and HDAC inhibitors in PDAC, (2) to resolve binding of novel PDI inhibitors to their target using X-ray crystallography, and (3) to demonstrate the preclinical anti-cancer activity of lead PDI inhibitors as single agents and in combination with HDAC inhibitors in genetically engineered mouse models (GEMMs) of PDAC. These aims are built on clear rationale from the existing literature and strong preliminary data. This work is innovative because we investigate the activity and mechanism of a new drug candidate and new treatment combination for the treatment of PDAC, a cancer in desperate need of new therapies. It is our expectation that this work will deliver a new drug candidate and combination treatment regimen for the treatment of PDAC, provide insight into the druggability of an emerging cancer drug target in PDI, and uncover molecular mechanisms that enhance the activity of HDAC inhibitors.